EFFECT OF COAL FLY ASH ON FROST RESISTANCE OF HOT MIX ASPHALT

Abstract

This paper presents the utilization of coal fly ash in pavement construction that acts as filler replacement which could improve the performance of its properties, particularly improving the foundation of road bases, which would be also considering the seasonal effects such as frost. Frost damage in cold regions is a phenomenon of great practical importance in highway engineering design and construction. One of the objectives of this study is to investigate the effect of coal fly ash (CFA) as a filler replacement on the mechanical properties of bitumen-aggregate mixtures at various percentages 1%, 2%, 3%, 4%, 5% and 6% by weight of aggregate. Freeze and thaw cycle test was conducted to simulate cold region countries condition, and compared with normal condition. Marshall Test was done to evaluate the suitability of coal fly ash as mineral filler for normal and frost conditions. Result obtained from test was compared between control sample and sample with CFA. Marshall Parameters can be improved by adding CFA as filler replacement to the HMA as compared to normal filler, although, results showed that by addition of CFA some specifications of ST RK 1218-2003 «Materials on the basis of organic binders for road and airfield construction. Test Methods» were not met requirements. It was observed that there was a definite increase in Marshall stability and decrease in flow values. Optimum CFA was determined to be in range of 1% to 3% by applying the range method. The mechanical properties, namely modulus of resilient and tensile strength were determined by carrying out modulus test and indirect tensile test respectively. The results revealed that the highest value of modulus of resilient for both conditions when CFA content was 3%. Indirect tensile test conducted for frost condition only and found that the highest value was in range of 2% to 3%.